1) Field of the Invention
This application is related to the field of current sensors.
2) Description of the Prior Art
Stray currents, especially 60 Hz currents, flowing on the grounding network of agricultural facilities may create zones of discomfort for the animals and cause physiological reactions of the animals resulting into abnormal health conditions.
The new technologies used to control electric motors which modify the level and the frequency of the current and the presence of electrical arcs on the distribution network of a farm are also among the factors that have direct consequences on the quality of the animal environment (see U.S. Pat. No. 6,690,565 B2).
Two types of variable speed motor controllers are frequently used in agricultural facilities. One is based on thyristors switched at a rate of 120 times per second while the other is composed of Insulated Gate Bipolar Transistor switched between 10000 and 20000 times per second.
The insulation of electric motor windings and also the insulation of the electric cables feeding the motors have capacitive reactance components in regard to the ground. These capacitive reactance components are responsible for current leaks when exposed to high frequency currents. The transmission modes of the leakage current are the same for the two technologies of motor controllers but the leakage will be more important in the case of the technology operating at higher frequencies.
The electrical arcs, in addition to being responsible of many fires, have important consequences on the animal environment because they produce harmonics of various levels and frequencies on the grounding network. Since electrical arcs may arise in every component of electrical networks, it is thus useful to monitor each component in order to perform early detection, characterize and predict any possible fault.